throttle body

Take the throttle body off and measure the size of the intake opening. It won't do any good to buy anything larger. Is the exhaust large enough to handle the increased flow?

there is also the issue of fuel pressure...wouldn't you be better off talking to a machinist for a second throttle body with a second injector?

^unless the throttle body/plate is a restriction causing drag. As tenspeed said, dont go bigger than the Intake manifold inlet for obvious reasons. The larger TB with also give you increased throttle response which is nice. On a side note, you 3 are post whores, arent ya?